How to dynamically extend class with method in TypeScript?

Question

How to dynamically extend class with method in TypeScript? Any examples? I try:

UsersBlocksMyOrders.prototype.myFunc = function():any{
  alert('23434');
};

But compiler give me a error.

Answer 1

Most often, you need to do something like:

interface UsersBlocksMyOrders {
    myFunc(): any;
}

Otherwise the compiler doesn't know about it.

---

It even works with existing classes. For example:

interface String {
    logit(): void;
}

String.prototype.logit = function () {
    console.log(this);
}

let a = "string";
a.logit();

(code in playground)

---

Because you want to change something in a different module, which is called Module Augmentation, you need to do something like:

Import { UsersBlocksMyOrders } from "../pages/users/blocks/myorders";

declare module "../pages/users/blocks/myorders" {
    interface UsersBlocksMyOrders {
        logit(): void;
    }
}

UsersBlocksMyOrders.prototype.logit = function () { console.log(this); }

Whenever possible (which it seems to be for you), edit the source code directly. Doing it like this should only be done on an as-needed basis.